The present invention pertains to a stone detection method and apparatus for detecting and removing discrete hard foreign objects from mobile agricultural equipment. Specifically, self-propelled combine harvesters and forage harvesters are adapted with an apparatus that performs the method of detection of rocks and other discrete hard objects to permit the reliable removal of rocks and foreign objects from harvested crop material during crop harvesting operations.
In the art of mechanically harvesting crops, it is known that self-propelled agricultural vehicles, such as combine harvesters and forage harvesters, are used to mechanically harvest crops. Typically, these vehicles are equipped with a harvesting implement, or header, that includes a reel for pulling crops into an array of blades for cutting the crop, wherein the cut crop material is pulled farther into the header by an auger. Once past the auger, the cut crop material is carried by an elevator to a threshing and sorting mechanism that removes unwanted chaff material from the desired crop matter before the crop matter reaches a storage compartment carried by the vehicle. However, this simple crop harvesting process is complicated by the fact that stones and other discrete hard objects are often pulled into the header with the crops. In the context of this disclosure, the terms xe2x80x9cstones,xe2x80x9d xe2x80x9crocks,xe2x80x9d xe2x80x9cobjects,xe2x80x9d and xe2x80x9chard materialsxe2x80x9d are used interchangeably and define equivalent matter to include any discrete undesirable matter such as stones, rocks, pieces of metal, and pieces of wood, that is separable from the cut crop material (i.e., harvested crop plant material). Unfortunately, stones and other hard debris can cause expensive damage to the elevator and threshing mechanisms; therefore, various methods and apparatuses have been developed to detect and remove stones and other potentially damaging foreign objects from the header before the cut crop material is carried by the elevator into the threshing and sorting mechanism.
Typically, the stone detection methods and apparatuses of the prior art include a stone detection circuit that operates a mechanism for removing any stones or hard objects. For example, U.S. Pat. No. 3,675,660 to Girodat, which is incorporated herein by reference in its entirety, discloses a rock detection circuit that includes a rock detector, a bandpass filter, a peak signal detector, an amplifier, and a solenoid operated trap door placed along the cut crop path before the crop elevator. The rock detector is a piezoelectric ceramic disc that picks up vibrations as the crop material passes and sends a sensing signal to the bandpass filter. Rocks are known to generate higher frequency vibrations than the crop material, so the bandpass filter removes low frequency signals from the sensing signal before sending the filtered signal to the peak signal detector. The peak signal detector generates a signal only if the filtered signal has an amplitude greater than a predetermined amplitude (xe2x80x9cthreshold amplitudexe2x80x9d), thereby filtering out background noise signals. When the filtered signal exceeds the predetermined amplitude, the peak signal detector generates a signal that is amplified by an amplifier, which sends an activating signal to a solenoid, which operates to open the trap door so that the hard foreign object will fall out of the header. Unfortunately, there is a lot of background noise due to vibrations generated by the vehicle""s engine, jarring of the vehicle as it travels along the ground, and rock impacts on the exterior of the header during harvesting operations. Consequently, unless sensitivity of the rock detection circuit is precisely set, either the trap door will open unnecessarily thereby spilling valuable crop on the ground or the trap door will not open when needed so that many large stones will reach the elevator and threshing mechanism resulting in damage to the vehicle. It is noted that Girodat""s rock detection circuit has no control components for adjusting the frequency sensitivity of the bandpass filter, or the threshold amplitude of the peak signal detector.
In an attempt to mitigate the effect of background vibrations, U.S. Pat. No. 4,275,546 to Bohman et al. discloses a stone discriminator circuit that uses a pair of piezoelectric crystals that are vibrationally isolated from the header and the harvester by two vibration isolators. The two piezoelectric crystals are set to detect different vibration frequencies, one crystal detects vibration generated by the crop material and the other crystal detects vibration generated by stones. Each crystal sends signals to its respective bandpass filter, then to a difference amplifier that receives input from both bandpass filters. The difference amplifier detects the difference between the signals from the two crystals and outputs an amplified signal to a threshold circuit. The threshold circuit generates a signal to operate a trap door or an alarm only if the amplified signal from the difference signal exceeds a threshold amplitude. In other words, the two crystals provide comparative information with respect to the background vibrations and superimposed rock vibrations in an attempt to weed out the background events from stone impact events near the crystals. However, Bohman""s circuit also has the drawback that the stone discriminator circuit has no control components for adjusting the frequency sensitivity of the bandpass filters, or the threshold amplitude of the threshold circuit.
Lastly, U.S. Pat. No. 4,720,962 to Klinner discloses a means for detecting stones and metal, which is a circuit including a vibration detector and a metal detector for detecting unwanted objects in a forage harvester. The vibration detecting portion of the circuit includes a vibration sensor, a high pass filter and a comparator, so that a vibration detecting signal is generated that is frequency filtered and that represents an event exceeding a minimum threshold amplitude. Input from a metal sensor and input from the vibration detecting portion feed into the remaining portion of the stone and metal detection circuit to activate a door system to get rid of the unwanted object. It is noted that the stone and metal detection circuit includes a timing circuit so that the door system stays open for only a predetermined period of time. However, Klinner""s stone and metal detection circuit has no control components for adjusting the frequency sensitivity of the bandpass filters, or the threshold amplitude of the threshold circuit.
Therefore, the present invention endeavors to provide an improved method for detecting and removing hard objects from cut crop material during crop harvesting with a mechanical harvester, and an apparatus for performing this method that reliably produces cut crop material that is essentially solely cut crop matter that is an improvement over the prior art devices and methods.
Accordingly, a primary object of the present invention is to overcome the disadvantages of the prior art methods and apparatuses for detecting and removing hard objects from cut crop material during crop harvesting with a mechanical harvester.
Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that achieves adequate detection rates for the hard foreign objects, so that the objects can be reliably removed.
Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that allows for external adjustment of various detection parameters by an operator to achieve the improved detection rates for the hard foreign objects.
Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that allows for the system to internally adjust to various internal and/or external influences that are transparent to the operator to achieve the improved detection rates for the hard foreign objects.
In accordance with the present invention, there is provided a method for detecting and removing hard objects from a cut crop material that is not limited to any one particular apparatus, or combination of apparatuses, for performing the method. The method comprises the steps of (a) providing a cut crop material that includes foreign hard objects in addition to cut crop matter; (b) sensing the cut crop material and foreign hard objects using a sensor to generate a signal; (c) amplifying the signal, wherein the magnitude of amplification is controlled by the microprocessor; (d) processing the signal to filter a bandwidth to generate a bandwidth filtered signal, optionally wherein a microprocessor controls the frequency range of the filtered bandwidths; (e) processing the bandwidth filtered signal to generate an amplitude threshold signal when the bandwidth filtered signal exceeds a minimum threshold amplitude, wherein the microprocessor controls a value of the minimum threshold amplitude; (f) processing the amplitude threshold signal to generate an internal signal only when the amplitude threshold signal has a pulse width that exceeds a minimum pulse width value, thereby eliminating noise signals; and (g) determining that a hard object is present based upon the internal signal, then removing the hard object based upon an output signal by using a hard object removal mechanism to produce a cut crop material that is essentially cut crop matter.
The present invention also provides an agricultural harvester having a header with a reel and an auger, wherein the reel and the auger provide crop material to an elevator and a foreign object detecting mechanism, wherein the foreign object detecting mechanism includes a foreign object detecting circuit to detect foreign objects and an object extrusion mechanism operationally connected to be activated by the detecting circuit, wherein the detecting circuit is connected to a power supply and comprises (a) a first vibration sensor that generates a first input signal in response to vibrations generated by a foreign object; (b) a programmable amplifier that receives the first input signal and generates an amplified first output signal; (c) a frequency bandpass filter that receives and filters a bandwidth of the first output signal to generate a first frequency filtered signal; (d) a variable threshold comparator that receives the first frequency filtered signal and generates a second output signal when the first frequency filtered signal exceeds a minimum threshold amplitude; (e) a pulse rejection network that deceives the second output signal and generates an internal signal when a frequency calculated from the pulse train of the second output signal corresponds to a specified frequency bandwidth; and (f) a microprocessor that includes the pulse rejection network and that is electronically connected to the threshold comparator and to the programmable amplifier, wherein the microprocessor operates to control the value of the minimum threshold amplitude of the threshold comparator and to control the magnitude of signal amplification performed by the programmable amplifier, wherein the detecting circuit activates the object extrusion mechanism whenever the detecting circuit generates a third output signal.